1. Technical Field
The present invention relates to an ultrasonic sensor, a measuring device, and a measurement system able to detect the position of an object to be detected using ultrasound.
2. Related Art
There are devices that use ultrasound to detect the state of an object to be detected such as a blood vessel in the human body (e.g., see Japanese Laid-Open Patent Application Publication No. 2005-34543).
The device described in Japanese Laid-Open Patent Application Publication No. 2005-34543 has a probe in which a transducer has been disposed longitudinally parallel to the axial direction of a blood vessel. From the probe, a blood vessel diameter-detecting ultrasonic beam is transmitted vertically with respect to the wall of the blood vessel and a speed-detecting ultrasonic beam is transmitted so as to intersect the axial direction of the blood vessel at an angle in order to measure the change in the blood vessel diameter and the blood flow over time.
However, in a device such as the one described in Japanese Laid-Open Patent Application Publication No. 2005-34543, the position of the blood vessel has to be accurately identified and the axial direction of the blood vessel has to be aligned with the direction of the transducer when blood flow and blood pressure are measured. If the user is a person with specialized knowledge such as a physician, the position of the blood vessel can be easily identified. However, it cannot be easily identified if the user is a person without specialized knowledge. Therefore, such a device is difficult to operate correctly if the user is a person without specialized knowledge, even though it can be easily operated by a person with specialized knowledge. When the condition of a blood vessel is to be measured continuously for 24 hours, the position of the blood vessel may shift. In these situations, the direction of the transducer cannot be set with respect to the axial direction of the blood pressure, and accurate measurement results cannot be obtained.
In response, a method for identifying the position of an object to be measured (e.g., see Japanese Laid-Open Patent Application Publication No. 2002-11008) and a method for measuring displacement of a blood vessel (e.g., see Japanese Laid-Open Patent Application Publication No. 2009-201557) have been proposed.
The device described in Japanese Laid-Open Patent Application Publication No. 2002-11008 is equipped with an ultrasonic probe in which transducers for detecting the position of a blood vessel are arranged in a two-dimensional array. In this device, ultrasound is transmitted directly below the transducers for detecting the position of a blood vessel, and ultrasound reflected by the blood vessel directly below the ultrasonic probe is detected to measure the position of the blood vessel.
In the configuration of the device described in Japanese Laid-Open Patent Application Publication No. 2009-201557, a single transducer is arranged on both ends of a probe for measuring blood flow to test for the position of maximum blood flow, and detect the position of the blood vessel.